extensions/av1: use -O2 for release builds
extensions/av1: use -O2 for release builds

+ force arm (over thumb) mode for 32-bit builds

-O2 improves performance ~30-40% over the default -Oz depending on the
resolution; this is similar to what is done for vp9 which uses -O3.

PiperOrigin-RevId: 290318121

ened/ExoPlayer,google/ExoPlayer,amzn/exoplayer-amazon-port,androidx/media,google/ExoPlayer,stari4ek/ExoPlayer,google/ExoPlayer,ened/ExoPlayer,amzn/exoplayer-amazon-port,stari4ek/ExoPlayer,androidx/media,ened/ExoPlayer,amzn/exoplayer-amazon-port,androidx/media,stari4ek/ExoPlayer